Testing the Simultaneity of Forbush Decreases with Algorithm-Selected Forbush Event Catalogue

TL;DR

This paper presents an automated method using Fourier transforms and detection algorithms in R to identify and catalog Forbush decreases in cosmic ray data, analyzing their simultaneity across multiple neutron monitors.

Contribution

The study introduces an automated, algorithm-based approach for detecting and timing Forbush decreases, including a cataloging system and analysis of event simultaneity across stations.

Findings

Detected over 4000 FDs with hourly data across three stations.

Identified 261 simultaneous FDs at all stations with hourly data.

Developed a reproducible R-based detection algorithm.

Abstract

Accurate detection and precise timing of transient events such as X-ray photons, {\gamma}-ray burst, coronal mass ejections (CMEs), ground level enhancements (GLEs) and Forbush decreases (FDs) frequently raise issues that remain on the cutting edge of research in astrophysics. In an attempt to automate FD event selection, a combination of Fast Fourier transform as well as FD detection algorithms implemented in the statistical computing software R was developed and recently used to calculate the magnitude and FD event timing. The R-FD code implemented in the present study includes several different calculations. Some subroutines detect both small and large transient intensity reductions (minima/pits) as well as increases (maxima/peaks) in cosmic ray (CR) data. Others calculate event amplitude, timing and cataloging of the events identified. As the current work focuses on reductions in CR flux (FDs), the subroutine that identifies increases was disabled. Totals of 229 FDs at Magadan neutron monitor (NM), 230 (Oulu NM) and 224 (Inuvick NM) were identified with daily averaged data, while 4032 (Magadan), 4144 (Oulu) and 4055 (Inuvick) were detected with hourly averages. FDs identified as simultaneous at the three stations totaled 99 for the daily and 261 for the hourly CR averages respectively.